32. Commission des “Selected Areas”

The Plan of Selected Areas was suggested by the late Prof. J. C Kapteyn in 1906. The aim of the plan is to bring together, as far as possible, all the elements which seem most necessary for a successful attack on the problem of the structure of the sidereal world. The first, second and third reports on the progress of the plan were published by the Kapteyn Laboratory in 1909, 1910 and 1923 respectively, the fourth report appeared in Bulletin of the Astronomical Institutes of the Netherlands, No. 211, 1930. Many observatories and astronomers have co-operated on the plan and for the northern hemisphere most of the work has been finished or is now in progress.</jats:p

33. Commission de la Statistique Stellaire

The following recommendations have been made:1. That a catalogue of the fainter stars with known proper motions or at least a list of the authorities of the proper motion of the fainter stars should be published (Van Maanen).2. That the parallax observers are requested to publish the basis of selection of the stars of their observing programme.</jats:p

33. Commission de la Statistique Stellaire

In the wide field of research covered by the Commission considerable progress has been made in recent years, and it is only possible here to touch briefly on the results of a few lines of investigation, without any attempt to completeness.Stellar luminosities. On the basis of the new list of Mount Wilson spectroscopic parallaxes and a compilation of the long series of modern trigonometric parallaxes A. van Maanen finds 617 objects within a distance of 20 parsecs from the sun. It is very doubtful, however, if we know all the stars even in the region of 5 parsecs radius. Almost all the known stars within 20 parsecs belong to the main sequence, the faintest star being of absolute magnitude +16.6. The most interesting deviations from the main sequence are the three “white dwarfs”, Сотр. of Sirius, Comp. o2 Eridani, and van Maanen’s F type star. G. P. Kuiper lists 3 additional white dwarfs at larger distances which were estimated to be of types Bo, B7 and A2. For the first two stars, A.C. 70°8247 and Wolf 1346, a revision of the spectral types by Adams and Humason gives A2 and A5, respectively, although the spectra differ considerably from normal ones. The A2 star in Kuiper’s list is the one discovered by Oosterhoff in the region of the cluster h, X Persei; its spectral characteristics have been examined by Öhman and by Humason. The absence of the high-numbered members of the Bahner series and of the continuous absorption at the Balmer limit seems to be an important criterion of such stars. A white dwarf of quite peculiar spectrum (type probably about B8) is the companion of o Ceti discovered spectro-graphically by Joy in 1922. There appear several additional deviations towards faint magnitudes from the main sequence which may be classed more or less safely among the white dwarfs. A few such cases have been discussed at Lund by J. Tuominen.</jats:p

32. Commission des “Selected Areas”

The following lines give a summary of the work concerning Kapteyn’s Plan of Selected Areas up to December 1937.</jats:p

Inhibition of cyclooxygenase-2 impacts chondrocyte hypertrophic differentiation during endochondral ossification

Skeletogenesis and bone fracture healing involve endochondral ossification, a process during which cartilaginous primordia are gradually replaced by bone tissue. In line with a role for cyclooxygenase-2 (COX-2) in the endochondral ossification process, non-steroidal anti-inflammatory drugs (NSAIDs) were reported to negatively affect bone fracture healing due to impaired osteogenesis. However, a role for COX-2 activity in the chondrogenic phase of endochondral ossification has not been addressed before. We show that COX-2 activity fulfils an important regulatory function in chondrocyte hypertrophic differentiation. Our data reveal essential cross-talk between COX-2 and bone morphogenic protein-2 (BMP-2) during chondrocyte hypertrophic differentiation. BMP-2 mediated chondrocyte hypertrophy is associated with increased COX-2 expression and pharmacological inhibition of COX-2 activity by NSAIDs (e.g., Celecoxib) decreases hypertrophic differentiation in various chondrogenic models in vitro and in vivo, while leaving early chondrogenic development unaltered. Our findings demonstrate that COX-2 activity is a novel factor partaking in chondrocyte hypertrophy in the context of endochondral ossification and these observations provide a novel etiological perspective on the adverse effects of NSAIDs on bone fracture healing and have important implications for the use of NSAIDs during endochondral skeletal development

25. Commission de Photométrie Stellaire

Much material extending our knowledge of stellar magnitudes has accumulated during the last four years. In the appendix to this report will be found a list of recent catalogues, a summary of the discussion made at Mt Wilson by Seares and the formulae that he finds for the reduction of these catalogues to a fundamental system, until such time as a more extended discussion shall have furnished definitive corrections.</jats:p

24. Commission des Parallaxes Stellaires et des Mouvements Propres

In November 1931 the President circulated a letter to the members of the Commission which in part was as follows:In view of the fact that it is now over a quarter of a century since Schlesinger by photography began to determine trigonometric parallaxes by a long focus telescope, and fifteen years since Adams and Kohlschütter derived the first spectroscopic parallaxes, it would seem appropriate to take stock of our present position and to make plans for future development.Will you be good enough, therefore, to furnish such statements concerning the following topics as are appropriate to the work of your observatory?</jats:p

24. Commission des Parallaxes Stellaires et des Mouvements Propres

Since the Paris meeting of the Union 3050 parallax plates have been secured and in the same interval 5604 plates have been measured and 182 parallaxes have been determined.</jats:p